Modern telecommunications equipment is increasingly utilizing underground vaults and conduits that are accessible by sealed manhole openings. Typically, the manhole opening consists of an annular frame attached to the telecommunications vault below grade. A circular disk provides a top cover to seal the annular frame from the elements and intrusion by people and animals.
Typical prior art manhole openings may also provide a gasket so rain water and contaminants do not enter the telecommunications vault. The gasket may be a loose gasket, a foamed in place gasket affixed to either the annular frame or the cover, or an O-ring.
Also known in the prior art is a system of two-cover manhole openings, such as a system sold by Neenah Foundry, specifically their R-1751 series telephone manhole frame with outer and inner lid. This type of manhole access system provides a level of water resistance and security to the telecommunications vault.
The Neenah Foundry product comprises an annular frame comprising a peripheral frame, with a top opening and a bottom opening. Also included are a top cover, a bottom cover, a crossbar, eyebolt, and a saddle. The top cover and bottom cover are circular disks with a top surface and a bottom surface. The bottom surface of the bottom cover engages a portion of the peripheral wall of the frame to seal the telecommunications vault below the manhole opening. In the middle of the top surface of the bottom cover is a threaded bore that extends a distance into the top surface of the bottom cover. Above the bottom cover, the crossbar is installed inside the annular frame and engages the peripheral wall. In the center of the crossbar is a threaded hole, which aligns with the concave feature in the bottom cover. The saddle is installed on top of the crossbar. The saddle is a U-shaped member and includes a slot through the base of the U. An eyebolt is threaded into the crossbar which applies pressure to the concave feature in the bottom cover. The U-shaped saddle is installed upside down, forming an n-shape, with the slot in the base aligned with the eyebolt in the crossbar, which locks the eyebolt in place. The shank of a padlock is passed through the eye of the eyebolt, which locks the saddle in place, preventing the eyebolt from turning. With the bottom cover now secured, the top cover can be installed over the top opening in the frame.
U.S. Pat. No. 4,101,236, entitled “SEALING MANHOLE COVER FOR USE ON EXISTING UNSEALED SANITARY SEWER MANHOLE COVER FRAME,” discloses a cover for an unsealed manhole that incorporates an O-ring on one surface to engage the frame, thus providing a seal. U.S. Pat. No. 4,101,236 does not provide protection against tampering or unauthorized entry. The present invention is not limited in this regard. U.S. Pat. No. 4,101,236 is hereby incorporated by reference into the specification of the present invention.
U.S. Pat. No. 5,328,291, entitled “LOCKING MANHOLE INSERT,” discloses a cover for a manhole frame that incorporates a plurality of radial arms that engage the peripheral wall of the annular manhole frame. The radial arms are secured with a padlock to prevent unauthorized entry and may be retracted for access. The present invention does not use radial arms as described in U.S. Pat. No. 5,328,291. U.S. Pat. No. 5,328,291 is hereby incorporated by reference into the specification of the present invention.
U.S. Pat. No. 5,827,007, entitled “ENTRANCE-DETERRING CAP FOR MANHOLE OPENINGS,” and U.S. Pat. No. 5,951,200, entitled “ENCLOSEMENT TO SHIELD STRUCTURE WHICH SECURES ENTRANCE-DETERRING CAP TO MANHOLE OPENING FROM WATER AND DIRT CONTAINMENTS,” discloses a cover for a manhole frame that seeks to prevent unauthorized access. The device disclosed provides an annular pan with a lip that engages the top of the manhole annular frame. Below the annular pan is an elongated bar that extends from one side of the peripheral wall to the opposite side. A threaded rod with a bore perpendicularly positioned relative to the length and series of nuts attaches the annular pan to the elongated bar, locking the two together. A padlock is used to lock the nuts to the threaded rod by passing the shackle through the bore in the threaded rod. The present invention does not use an annular pan or specialty threaded rod as described in U.S. Pat. No. 5,827,007 and U.S. Pat. No. 5,951,200. U.S. Pat. No. 5,827,007 and U.S. Pat. No. 5,951,200 are hereby incorporated by reference into the specification of the present invention.
U.S. Pat. No. 7,178,290, entitled “MANHOLE COVER HAVING A LOCKING CROSSBAR,” discloses a rectangular pit cover having a small hinged opening for access to padlockable crossbar. The crossbar engages the peripheral walls of the pit cover frame, much like the peripheral wall of the manhole frames described above and is used to prevent unauthorized removal of the pit cover. The small hinged opening does not lock or require tools to open, providing an easy opportunity for tampering. The device described in U.S. Pat. No. 7,178,290 also requires modified manhole covers, increasing the cost of adoption. The present invention does not use a hinged opening within the outer cover for gaining access to a padlocked crossbar as described in U.S. Pat. No. 7,178,290. U.S. Pat. No. 7,178,290 is hereby incorporated by reference into the specification of the present invention. There exists a need to secure manhole covers with an enhanced security device that does not damage the padlock and is inexpensive to retrofit to existing manhole frames.